Process for the treatment of aluminum



Patented Oct 13, 1931 UNITED: STATES PATENT OFFICE MARTIN KRISTENSEN DE TRAIBUP, OF LONDON, ENGLAND PROCESS FOR THE TREATMENT OF ALUMINUM No Drawing. Application filed December 4, 1929, Serial No. 411,697, and in Great Britain September This invention relates to a process for preparing the surface of aluminum for receiving subsequent treatment of the nature of electro-plating, dry-tinnin and soldering. V In the preferred form 0 the invention the amalgam is deposited on to the aluminum surface in an electrolytic bath containing a solution of salts of mercury and tin.

In another form of the invention, the amalgam is deposited on to the aluminum surface in an electrolytic bath containing a solution of salts of mercury in combination with other metals particularly tin and zinc.

For general purposes a bath composed, for example, of :caustic soda, sodamide or the constituents thereof, tin chloride, zinc chloride, mercury nitrate, pure potassium hydroxide in water, may be employed,

According to the nature of the subsequent process to which the aluminum is to be subjected and to whether the aluminum is pure or in the form of an alloy, the constitution of the bath in which the amalgam is deposited, the time for which the electro deposition is continued and the strength of the current supplied are varied.

After treatment -'n the bath the aluminum surface is cleaned and is then ready for the subsequent treatment. If it is then desired to tin the aluminum, the article is dipped in the usual way in a bath of molten tin which adheres firmly to its surface or it may be heated and covered 7 or sprinkled with one of the many tin compounds on the market with the same result, or it may be tinned by rolling a thin deposit of tin on the surface.

If it is desired to solder the aluminum after it has been subjected to the preliminary treatment, this can be done in the usual way with tin solder or any tin soldering compound on the market.

When the treated aluminum is to be plated 5 with a final coating of metal, this is carried out in the usual way in a plating vat.

A suitable composition of the preliminary bath for use in the case when the aluminum is pure aluminum and is to be nickel-plated after treatment in the preliminary bath acso that the presence of the metallic salts cording to the invention is for example the following 200 grammes caustic soda 10' grammes pure potassium hydroxide in 20 litres of water.

The article is cleaned and pickled in the usual manner and is then placed in the above mentioned preliminary bath for a. few min utes under a current of 1.5 volts. The mercuryis so distributed in the bath by thechemicals that the coating deposited on the aluminum article by the current is absolutely-even. The mercury has the prop erty,,together' with the other chemicals, of 0 dissolvingthe metal, and is evenly distributed overthe wh'olesurfaceof the aluminumby the current, seals up any existing pores and combines homogeneously with the aluminum,

particularlylztin'c and tin in the bath a relatively strongdeposit can bebbtained. p

With mercury al0ne,7too weaka deposit wouldbeobtained; the problem consists essentially in forming'a homogenous union;

The. article is then taken out of the bath,

rinsed with water and hung in thefinalbath of nickel, copper, goldaorsilver, for example,

where it is provided with the final coating. ,g;

On account of the provision of the intermediate ].ayer, this coating adheres extremely fast, so that even when subjected to sudden heating and cooling or rough mechanical treatment the coating does not become de-,,e0

I claim as new and desire to secure by Letters Patent is 1. A process for preparing the surface of aluminum for receiving subsequent treatment of the nature of electro-plating, dry-tinning and soldering, consisting in depositing an amalgam on to the aluminum surface in an electrolytic bath containing a solution of salts of mercury and tin.

2. A process for preparing the surface of aluminum for receiving subsequent treatment,

of the nature of electro-plating, dry-tinning and soldering, consisting in depositing anamalgam on to the aluminum surface electrolytically in a bath containing a solution of salts of mercury in combination With other metals, particularly tin and zinc.

3. A process for preparing the surface of aluminum for receiving subsequent treatment of the nature of electroplating, dry-tinning and, soldering, consisting in depositing electrol tically an amalgam on to the aluminum surface in a bath composed of :ca-ustic soda, sod amide, tin chloride, zinc-chloride, mercury nitrate, pure potassium hydroxide in Water.

4. A process for preparing the surface of aluminum for receiving subsequent treatment of the nature of electroplating, drv-tinning and soldering, consisting in depositing; electrolytically amalgam to the aluminum surface in abath composed of:

200 grammes caustic soda 200 grammes sodamide 40 grammes tin chloride 10 grammes "zinc chloride 5 grammes mercury nitrate 1O grammesuflpure potassium hydroxide V in 20 litres of water.

5. A process for plating aluminum consisti-ng infirst depositing an, amalgam, on. an aluminum, surface electrolytically in a bath containing a solution of salts of mercury in combination with other metals, particularly tin and zinc, and inthen applying the final plating metal thereon.

In testimony whereof I have signed my name to this specification.

MARTIN KBISTENSEN DE TRAIRUP. 

